Volcano and Volcanism

• Volcano


  -place on Earth’s surface (or any other planet’s or moon’s) where

  molten rock, gases, and pyroclastic debris erupt through the earth’s crust

  -can be a mountain, a vent, or caldera
• Volcano etymology

  Vulcan – Roman god of fire

  Vulcan was said to have had a forge on Vulcano, an active volcano on the Lipari Islands in Italy
• Why do volcanoes erupt?

  -due to decompression

  -magma is lighter than the solid around it (magma rises
• Types of Volcano: Shield


  -slopes are gentle (2°-10°)

  -shape resembles a Roman shield lying on the ground

  -made up of successive lava flows

  
• Type of Volcano: Cinder cones


  -relatively small (<300m high)

  -steep slopes (30°-40°); made up of pyroclastic materials

  
• Type of Volcano: Composite / Strato-volcano


  layered structure of alternating tephra and lava flows

  
• Distribution of volcanoes


  pacific ring of fire

  hot spots

  spreading centers
• Volcanic Explosivity Index (VEI)


  based on number of things (plume height, volume of ejecta, etc) that can be observed during an eruption
• Volcanic eruption: Hawaiian


  -calmest eruption type

  -characterized by the effusive emission of highly fluid basalt lava flows with low gas content

  -steady lava fountaining and the production of thin lava flows

  -Magma: FLUID

  -Effusive Activity: then, often extensive flows

  -Ejecta: cow-dung bombs and splatter, very little ash

  -Structure(s): spatter cones and ramparts, very broad, flat lava cones

  • Aa flows – jagged, rough blocks
  • Pahoehoe flows – smooth surfaces
• Volcanic eruption: Strombolian


  -short-lived, explosive outburst of pasty lava

  ejected a few tens or hundreds of meters into the air  no sustained eruption column

  -episodic explosions with booming blast  Magma: moderately fluid

  -Explosive Activity: weak to violent ejection of

  pasty fluid

  -Effusive Activity: thicker, less extensive flows,

  flows may be absent Ejecta: spherical to fusiform bombs; cinder; small

  to large amount of glassy ash

  -Structure(s): cinder cones
• Vulcanian volcanic eruption


  -Occur as a series of discrete, canon-like explosions that are short-lived, lasting for only minutes to a few hours, often with high-velocity ejections of bombs and blocks

  -Once the volcano "clears its throat" subsequent eruptions can be relatively sustained and quiet
• Vulcanian eruptions


  • More explosive than Strombolian eruptions with eruptive columns reaching 5 to 10km
  • Magma is viscous
  • Moderate to violent ejection of solid hot fragments of new lava
  • Flows commonly absent, thick and stubby if present
  • Ejecta are essential, glassy to lithic, blocks and ash, pumice
  • Structures include ash cones, block cones, block-and-ash cones
• Volcanic eruption: Peleean


  -Magma: viscous

  -Explosive Activity: like Vulcanian, commonly with glowing avalanches

  -Effusive Activity: domes and/or short, very thick flows, flows may be absent  Ejecta: same as Vulcanian

  -Structure(s): ash and pumice cones, domes
• Volcanic eruption: Plinian


  -generate sustained eruptive columns, with some reaching heights of ~45km

  -eruptive columns produce widespread dispersal of tephra which covers large areas with an even thickness of pumice and ash

  -Magma: viscous

  -Explosive Activity: ejection of large volumes of ash; caldera collapse

  -Effusive Activity: ash flows, small to very luminous, may be absent ---Ejecta: glassy ash and pumice

  -Structure(s): widespread pumice lapilli and ash beds, generally no cone-building
• Volcanic eruption: Surtseyan / Phreatomagmatic


  -generated by the interaction of magma with either groundwater or surface water

  -much more explosive; as the water is heated, it flashes to steam and expands explosively, thus fragmenting the magma into exceptionally fine-grained ash
• PhiVolcs Volcanic classification


  Active volcano

  • erupted with historical times (within last 600 years); accounts documented by man
  • erupted within the last 10, 000 years based on analyses of materials from young volcanic deposits
• PhiVolcs Volcanic classification

  Potentially-active volcano

  • Morphologically young-looking but with no historical or analytical records of eruption
• PhiVolcs Volcanic classification


  Inactive volcano

  • No recorded eruptions; physical form has been intensively weathered and eroded, bearing deep and long gullies
• Volcanoes in the Philippines

  24 active volcanoes based on eruptive history according to

  PHIVOLCS

  • PHIVOLCS – Philippine Institute of Volcanology and Seismology
• Mayon Volcano


  Albay

  54 known eruptions

  yearly volcanic activity

  1814: most destructive (VEI : 4)
• Taal Volcano


  Batangas

  39 known eruptions (1911 eruption)

  yearly volcanic activity
• Kanlaon Volcano


  Negros

  26 recorded eruptions

  continuously monitored
• Bulusan Volcano


  Sorsogon

  17 recorded eruption

  continuously monitored
• Hibok-hibok Volcano


  Camiguin

  5 recorded eruptions
• Mt. Pinatubo


  Zambales

  once classified as inactive until the 1991 eruption
• Monitoring volcanic eruptions


  Remote Sensing

  Geophysical measurement

  Geochemical sampling of gas and water

  Increase in earthquake occurrences

  Ground deformation
• Volcanic hazards: Volcanic gases (SO2, CO2, HCL)


  can cause health problems

  SO2 + H2O produces fine aerosols (fine droplets) that block the sunlight

  SO2 produces acid rain
• Volcanic hazards: lava flow

  destruction of lives, livelihood, and property
• Volcanic hazards: pyroclastic flows


  hot, dry rock fragments

  destruction of lives, livelihood, and property
• Volcanic hazards: Lahar

  mixture of water and rock fragments
• Volcanic hazards: Tephra


  volcanic rocks blasted in the air

  obscure sunlight, impassable roads, infrastructure damage
• Benefits of Volcanic Eruption

  Fertile agricultural lands

  Geothermal energy

  • Philippines ranked 3rd in power generation (1, 935 MW)
• Geothermal plants in the Philippines

  identify

  A) mt. labo

  B) mak-ban, laguna

  C) northern negros occidental

  D) tiwi-albay, camarines norte/sur

  E) panlipininon, negros oriental

  F) sorsogon albay

  G) tangonan leyte

  H) mt. caballian, so, leyte

  I) mt. apo, northern cotabato/davao